Pneumatic tires are typically comprised of carcass, tread and sidewall portions. The carcass portion has one or more layers of rubberized fabric or metal usually in a cord or cable form and is generally considered the foundation structure for the tire. The carcass portion usually terminates at and thus includes a pair of axially spaced annular bead portions stiffened by rigid and inextensible bead rings to secure and maintain the tire on a wheel and pneumatically seal the tire with the wheel. The tread portion is typically an elastomeric composition of suitable abrasion resistance and is integrated with the tire carcass along the crown thereof to provide the ground engaging surface for the tire. A breaker or belt assembly may be provided between the crown portion of the carcass and the tread and, depending upon the type of tire being built, may be initially assembled with either the carcass or the tread. The sidewall portions are typically of an elastomeric composition more flexible than the tread composition and join the bead portions to the tread.
Pneumatic tires are categorized as radial or bias type depending upon whether the direction of reinforcing cords in the carcass plies is radial or bias to the axial centerline of the tire. Tires of the bias type have been built by the "flat band" method utilizing equipment such as that described in U.S. Pat. Nos. 2,614,951, 2,614,952, 2,628,652, 3,171,769, 3,156,601, and 3,645,826, all of which are owned by the assignee of the present application. Tires of the radial ply type have been built by the "toric match" method using equipment such as that described in U.S. Pat. No. 3,475,254, which is also owned by the assignee of the present application.
The building techniques for building both radial and bias ply tires are similar in that principal portions or all of the tires are built on one or more expandable-collapsible cylindrical drums. After the building of the carcass, the tread-breaker assembly or the complete tire, the drum is collapsed and the tire component or finished tire removed typically by hand and transported to another station for further assembly or for cure. However, off-the-highway pneumatic tires for tractors, road graders, earthmovers and the like are too large and massive for simple manual transfer from and between building drums. Dismounting and transporting means such as that described in U.S. Pat. No. 3,787,262 can be used for these "giant" sizes.
A problem with such off-the-highway tires and particularly radial ply off-the-highway tires is that the tires do not have sufficient strength to support themselves in an uninflated and uncured or "green" state. Distortion under force of its own weight can severely degrade the quality of the tire produced. The tire cannot, therefore, be directly dismounted and transported by simply fastening the tire or tire carcass to, for example, an overhead crane. For this reason, the production of off-the-highway tires and particularly radial ply off-the-highway tires is extremely difficult, expensive and time consuming, and even then, the quality and quantity yields of the tires produced have not been completely satisfactory.
One method of producing off-the-highway bias ply tires has been to build the entire on one building drum. After the carcass is assembled, the tread is applied by strip treading procedures such as those described in U.S. Pat. Nos. 3,716,442, 3,177,918, 3,223,572, 3,251,722, 3,268,380 and 3,418,191. The assembled tire is then removed from the tire building machine by rotation of the axis of the building drum to a vertical position and removing the tire and drum together from the tire building machine (see, for example, U.S. Pat No. 3,787,262). The drum can then be conveniently removed from within the tire. It has been found, however, that such tires can become undesirably distorted by their own weight when placed in an axially vertical position. Such distortion may occur with massive tires of multiple plies in the carcass. With radial ply and/or wire tire constructions, the potential distortion is accentuated and more severe.
The present invention overcomes these difficulties and disadvantages of known tire building systems and apparatus. The present invention provides for the building, transporting and curing of giant off-the-highway pneumatic tires effecting improved qualitative and quantitative yield.